The present invention relates to a vibration damper for a vehicle, in particular for a motor vehicle.
German patent document DE 10 318 537 B4 describes a conventional attachment of a damper cylinder to a wheel carrier, which attachment is provided by screw and clamping connections.
German patent document DE 10 2011 084 475 A1 describes an integral pivot bearing made of cast aluminum. Here, both the damper integrated in the pivot bearing and the pivot bearing itself are formed from cast aluminum.
German patent document DE 10 2009 029 299 A1 describes an arrangement which is produced completely from fiber-reinforced plastic. Here, both the wheel carrier and the damper are produced from fiber-reinforced plastic. Both components are integrally bonded to one another.
The object of the present invention is to provide a vibration damper for a vehicle which, with economical production and simple assembly, is very lightweight and can be operated in a durable manner.
This and other objects are achieved by a vibration damper for a vehicle, preferably for a motor vehicle, comprising a wheel carrier made of metal for rotatably receiving a wheel, a damper tube arrangement made at least in part of fiber-reinforced plastic for forming a damper fluid volume, and a piston guided in the damper tube arrangement. The piston has a piston rod, wherein the damper tube arrangement is fixedly connected to the wheel carrier, and wherein the piston rod can be connected to a body of the vehicle. A wheel carrier fluid volume is formed in the wheel carrier and is connected to the damper fluid volume. The fluid in the wheel carrier fluid volume is in direct contact with the metal of the wheel carrier for a transfer of heat.
Within the scope of the invention it has been found that although the complete construction of the wheel carrier and of the damper tube arrangement from fiber-reinforced plastic is very lightweight, the heat produced in the damper cannot be dissipated very effectively. Furthermore, it should be noted that the complete construction of the vibration damper from metal material is very heavy. The conventional connection of the damper tubes to the wheel carrier via screw-connection interfaces also leads to additional weight and assembly effort.
In accordance with the invention, a vibration damper for a vehicle which includes a wheel carrier made of metal is therefore provided. The wheel carrier serves to rotatably receive the wheel. A wheel bearing is provided in or on the wheel carrier, accordingly. Furthermore, the vibration damper includes a damper tube arrangement. The damper tube arrangement is at least partly made of fiber-reinforced plastic. The damper tube arrangement provides a damper fluid volume. In particular, oil is used as fluid. A piston is guided in the damper tube arrangement. The piston is connected to a piston rod. The piston moves in the damper fluid volume. The damper tube arrangement is fixedly connected via its lower end to the wheel carrier. The piston rod constitutes a connection to the body of the vehicle. In addition to the damper fluid volume in the damper tube arrangement, a wheel carrier fluid volume is formed directly in the wheel carrier. The fluid, in particular the oil, in the wheel carrier fluid volume is connected to the damper fluid volume so that, in particular by way of movement of the piston, there is an exchange of fluid between the damper fluid volume and the wheel carrier fluid volume. The fluid in the wheel carrier fluid volume is in direct contact with the metal of the wheel carrier. A transfer of heat from the fluid to the metal wheel carrier is thus ensured.
By means of the at least partial formation of the damper tube arrangement from fiber-reinforced plastic, the potential for a lightweight construction is fully exploited. In order to also, at the same time, dissipate the heat produced in the fluid, the wheel carrier fluid volume is provided. The full mass of the wheel carrier can thus be used for dissipation of the heat.
The wheel carrier is preferably formed as a pivot bearing. The pivot bearing is a relatively bulky component, which constitutes a direct connection of the wheel bearing to the body. The pivot bearing thus combines the functions of the wheel carrier and the attachment of the wheel carrier to the body. In particular, this bulky component can be effectively used for the dissipation of the heat from the fluid.
The damper tube arrangement is preferably open at the end face so that the damper fluid volume transitions directly into the wheel carrier fluid volume. The end face of the damper tube arrangement can also be referred to as the base. This base of the damper tube arrangement is therefore open. The base of the vibration damper is therefore formed by the metal material of the wheel carrier. In particular, heat is thus transferred via the base.
Provision is furthermore preferably made for the wheel carrier fluid volume to constitute an extension of the damper tube arrangement so that the piston, depending on position, is moved through the damper fluid volume or the wheel carrier fluid volume. Not only the base, but also a cylindrical wall region of the vibration damper is therefore formed by the metal material of the wheel carrier, whereby the surface for heat transfer is enlarged.
Provision is furthermore preferably made for the vibration damper to include a base valve. A base valve of this type is used both in the case of a two-tube damper principle and in the case of a single-tube damper principle. This base valve is preferably arranged in the wheel carrier fluid volume, that is to say within the wheel carrier.
In accordance with a first preferred variant, a two-tube damper principle is applied. Accordingly, the damper tube arrangement comprises an outer tube and an inner tube. A compensation fluid volume is formed between the outer tube and the inner tube. The fluid can flow from the inner tube into the compensation fluid volume via the base valve. The inner tube advantageously protrudes further into the wheel carrier than the outer tube. In the region of the damper fluid volume, an outer wall of the compensation fluid volume is formed by the outer tube. In the region of the wheel carrier, the metal material of the wheel carrier itself forms the outer wall of the compensation fluid volume.
In accordance with a second preferred variant, a single-tube damper principle is used. Accordingly, the damper tube arrangement comprises just one individual tube. A compensation fluid volume is likewise required also in the case of use of the individual tube. In this arrangement as well, a base valve is preferably used, wherein the fluid can flow into the compensation fluid volume via the base valve. Provision is preferably made within the scope of the invention for this compensation fluid volume to be formed in the wheel carrier so that, in the compensation fluid volume, the fluid is in direct contact with the metal material of the wheel carrier. In particular, there are fluid channels below the base valve, which connect the wheel carrier fluid volume to the compensation fluid volume.
Cooling ribs are preferably arranged in the compensation fluid volume, wherein the cooling ribs are integral parts of the metal wheel carrier. These cooling ribs can be used both in the case of this single-tube damper principle and in the case of the two-tube damper principle. The cooling ribs significantly increase the surface areas for heat transfer.
Provision is preferably furthermore made for the outer tube (in the case of the two-tube damper principle) or for the individual tube (in the case of the single-tube damper principle) to be adhesively bonded to the wheel carrier.
In order to form the wheel carrier fluid volume, a blind bore or an accordingly shaped pocket is preferably formed in the wheel carrier. The damper tube arrangement is preferably inserted into this pocket or bore.
For the at least partial construction of the damper tube arrangement from fiber-reinforced plastic, a number of preferred variants are provided: provision is made for the inner tube, the outer tube and/or the individual tube to be made either completely of fiber-reinforced plastic or for a metal tube or plastic tube to be used, around which there is wound a fiber-composite material. Here, the metal or plastic tube serves in particular to guide the piston and is so weak that it is not durable without the external winding made of fiber-composite material. In particular, a fiber-reinforced plastic is wound around the metal or plastic tube.
In the case of the embodiment as the two-tube damper principle, it is also possible to form merely the outer tube at least partly in a fiber-reinforced manner and to use a tube made completely of metal for the inner tube.
In particular, with use of the above-described compensation fluid volume, provision is made for a compressible medium, in particular gas, for example air, to be arranged in the compensation fluid volume.
The used piston has a certain cross-sectional area, which corresponds substantially to the cross-sectional area of the inner tube or of the individual tube. The design of the wheel carrier with the wheel carrier fluid volume and the advantageous compensation fluid volume within the wheel carrier provides a certain heat transfer area, over which the fluid is in direct contact with the metal material of the wheel carrier. Provision is advantageously made for the heat transfer area to correspond to at least 150%, advantageously at least 200%, particularly advantageously at least 300% of the defined cross-sectional area of the tube. A sufficient heat-transfer area for the dissipation of heat from the fluid, in particular the oil, is thus provided.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.